Source shot noise mitigation in focused ion beam microscopy by time-resolved measurement.

Area of Science:

• Materials Science
• Microscopy Techniques
• Image Analysis

Background:

• Focused ion beam microscopy (FIB) is limited by source shot noise and secondary electron detection variability.
• These noise sources increase measurement variance, compromising the balance between ion dose and image accuracy in FIB imaging.
• Current methods lack sufficient time resolution to effectively address these inherent noise factors.

Purpose of the Study:

• To investigate methods for improving image accuracy in focused ion beam microscopy by addressing source shot noise.
• To introduce and evaluate time-resolved measurement processing techniques for FIB microscopy.
• To quantify the potential improvements in mean-squared error (MSE) and required ion dose.

Main Methods:

• Theoretical analysis of noise sources in FIB microscopy.
• Monte Carlo simulations to model time-resolved measurements.
• Development and application of three distinct data processing methods for time-resolved data.
• Experimental validation using a helium ion microscope.

Main Results:

• Three novel processing methods for time-resolved FIB measurements demonstrate significant mean-squared error (MSE) improvements over conventional methods.
• Maximum likelihood estimation offers an MSE reduction or dose reduction factor approximately equal to the secondary electron yield.
• Experimental results with a helium ion microscope confirm theoretical predictions, showing an accuracy improvement factor of approximately 4 for a fixed ion dose.

Conclusions:

• Processing time-resolved measurements in FIB microscopy effectively mitigates source shot noise and improves image accuracy.
• Maximum likelihood estimation provides a substantial improvement, comparable to complete noise mitigation.
• The findings suggest a practical approach to enhance FIB imaging performance, enabling higher accuracy at lower ion doses.